About region dimension
All regions have the property of dimension, which must be 2D or 3D. There is a significant difference between 2D and 3D regions in Echoview.
2D Regions are defined by a series of points in depth-time space and are intended for use on single beam, split beam or dual beam echograms. Their definitions can be exported to a single evr format file which can be imported to a new EV file if desired. They can be used to group single targets defining fish tracks.
3D regions are defined by a series of points in three dimensional space intended for use on multibeam echograms and scenes. Their definitions can be exported individually to wrl format files. These cannot currently be imported into EV files.
3D regions are a type of 3D object, 2D regions are not. Both 2D and 3D regions are displayed on the Regions window and in the Region Browser dialog box.